The present invention relates generally to electrostatic discharge protection devices. More particularly, the invention relates to electrostatic discharge protection devices for semiconductor chip packages ("SCP") where the electrostatic discharge protection device connects selected pins on the SCP so they are grounded or maintained at the same electrical potential to inhibit electrostatic charge accumulation when the SCP is not mounted on a receptor such as a circuit board, and disconnects the ground connection upon operative combination of the SCP on the receptor.
Electrostatic charge is a stationary electric charge which accumulates on various surfaces. An electrostatic discharge occurs when the electrostatic charge becomes substantial enough to overcome a dielectric material between the charge and another surface of lower electrical potential. An example of such a discharge as naturally occurring is lightning.
Electrostatic discharge in the realm of electronics can be devastating to microelectronic devices. A sharp voltage spike caused by an electrostatic discharge can cause permanent and costly damage to individual precision devices, such as random access memory inter alia.
Many commercially available electrostatic discharge protection devices in use today consist primarily of electrostatic discharge packaging of the SCP in electrically conductive strips, pellets, boxes, and plastic tubing which provide effective electrostatic discharge protection until a user is ready to insert the SCP into complementary receptacles on the circuit board or other interconnector. At that point the user must remove the electrostatic discharge protective packaging from the SCP, thus rendering the SCP vulnerable to electrostatic discharge, in order to position and insert connector pins of the SCP into receptacles. Accordingly, as the user inserts the connector pins of the SCP into the receptacles, the semiconductor die housed within the SCP's could be destroyed by electrostatic discharge and the SCP would therefore have to be replaced.
Moreover, certain types of SCP's, typically EPROM's, UVPROM's, and Dram's are plug-in devices which have connector pins which are repeatedly inserted into and later removed from the receptacles. These types of SCP's require electrostatic discharge protection during the repeated insertions into and removal from the receptacles. Specifically, the connector pins of those SCP's require electrostatic discharge protection from the moment that their connector pins are removed from their receptacles until their connector pins are again inserted therein.
Consequently a need still exists within the semiconductor chip packaging industry for a true electrostatic discharge protection device, rather than electrostatic discharge protection packaging, which effectively protects the semiconductor die from electrostatic discharge until the connector pins of the SCP are inserted into the receptacles of the connector and then protects the semiconductor die from electrostatic discharge again when the connector pins are removed from the receptacles.
A prior art electrical connector-receptacle arrangement is described in commonly assigned U.S. Pat. No. 5,108,299 entitled "Electrostatic Discharge Protection Devices for Semiconductor Chip Packages" by David V. Cronin issued Apr. 28, 1992, which shows a shunt attachment placed on pins of the semiconductor chip package arranged to provide a short circuit across selected pins. Upon insertion into the receptor, the attachment is driven away from the semiconductor chip package, causing the short circuit to be broken. While this arrangement is an improvement and is useful for connectors for semiconductor chip packages such as Dual In-line Packages ("DIP"'s), the design is relatively expensive to manufacture. The resilient conductive metal structure secured to the DIP with an adhesive can become too costly for use with inexpensive semiconductor chip packages.
Other commonly assigned patents and copending applications include U.S. Pat. No. 4,971,568 entitled "Electrical Connector With Attachment For Automatically Shorting Select Conductors Upon Disconnection of Connector" by David V. Cronin issued Nov. 20, 1990, U.S. Pat. No. 5,163,850 entitled "Electrostatic Discharge Protection Devices For Semiconductor Chip Packages" by David V. Cronin issued Nov. 17, 1992, U.S. Pat. No. 5,164,880 entitled "Electrostatic Discharge Protection Device for a Printed Circuit Board" by David V. Cronin issued Nov. 17, 1992, pending U.S. application Ser. No. 08/234,917 entitled "Electrostatic Discharge Protection Device" by David V. Cronin filed Apr. 28, 1994, and pending U.S. applications Ser. No. 08/278,024 and Ser. No. 08/278,063 each entitled "Electrostatic Discharge Protection Device" by David V. Cronin filed Jul. 20, 1994.
For the use of electrostatic discharge protection devices to be economically feasible, its cost must be relatively low compared to the value of the semiconductor device on which it is used. Devices in the above patents are of all metal construction and while they perform the electrostatic discharge protection task exceedingly well, the cost of such devices tend to preclude their use on lower-cost semiconductors which represent a large segment of the market.
Therefore, there is a need for a substantially lower cost electrostatic discharge protection device and it is an object of this invention to provide such a lower cost electrostatic discharge protection device.
Accordingly, it is an object of this invention to provide electrostatic discharge protection devices which operate to automatically open a short between selected conductors upon connection with a mating receptacle.
It is another object of the invention to provide an electrostatic discharge protection device which is inexpensive to manufacture.
These and other objects of the invention will be obvious and will appear hereinafter.